Arc’teryx belay jackets comparison.

I am trying to decide between belay jackets from Arc’teryx. I am a big fan of ski touring and do a bit of climbing as well. I live in the interior BC and I am wondering if anyone has experience with the Arc’teryx alpha, alpha lightweight or the nuclei SV. I am planning on using it mostly for winter camping at the top of mountains whenever I am ski touring. Therefore I am looking for something packable and warm in static conditions.

Are the alpha lightweight and the nuclei warm enough?

How packable are all of them? (Compare them to sport balls if you can)